Dynamoelectric machine



April 1943- L. GRIFFITHS DYNAMO-ELECTRIC MACHINE Filed Aug. 14, 1941 2 Sheets-Sheet l Inventor 3 Leonard Griffiths,

Hls Attorneg.

April 20, 1943. L IFFITH 2,317,187

DYNAMO-ELECTRIC MACHINE Filed Aug. 14, 1941 2 Sheets -She9t 2 V12. 4-. Flg. 5. f 1 1 Inventor '1 Leonard Griffiths,

b His Attorney. J

Patented Apr. 20, 1943 DYNAMOELEOTRIC MACHINE Leonard Griffiths, Coventry, England, assignor to General Electric Company, a corporation of New York Application August 14, 1941, Serial No. 406,761 In Great Britain January 14, 1941 7 Claims.

My invention relates to dynamo-electric machines, and although not limited thereto it has application to magnetos for producing electric ignition for internal combustion engines.

An object of my invention is to provide an improved dynamo-electric machine which will be efllcient in operation and compact in design.

Another object of my invention is to provide a magneto of improved design which will produce a large number of flux reversals through the coil member for each rotation of the rotatable member.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawings, and the features of novelty which charactteri'ze my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawings, Figs. 1, 2, and 3, diagrammatically illustrate a magneto provided with an embodiment of my invention, the different figures illustrating difierent relative positions of the rotatable member during a quarter of a revolution thereof; Figs. 4, and 6 illustrate a modification of the magneto illustrated in Figs. 1, 2 and 3,

and Fig. 7 illustrates a modification of the magneto illustrated in Figs. 1 to 6.

In the arrangements illustrated in the drawings, I have illustrated my invention as applied to magnetos for producing electrical ignition power for internal combustion engines. However, it is to be understood that my invention has application to a magneto of the speed indicating type, or to any other suitable type of dynamoelectric machine. The magneto includes a rotatable permanent magnet having a plurality of spaced apart pole pieces and a core member having a plurality of spaced apart pole faces which are adapted to cooperate with the pole pieces upon relative rotation therebetween. The

- core member has a portion magnetically coupled with a coil member and the pole faces are disposed with respect to the pole pieces such that twice the number of flux reversals through the coil member are obtained for one complete revo-' '2l for rotatable movement about an axis 21a which forms the center of the pole faces of the arms [2 and I3. An inductor structure of magnetic material is arranged to extend from each end of the magnet and includes outwardly extending portions 22 and 23 which are mounted on the shaft 2| and are held tightly against one end of the magnet 20. Pole pieces 24 and 25 formed of suitable magnetic material are provided which extend axially from the portions 22 and 23, respectively, so that they may cooperate magnetically with the pole faces upon relative rotation therebetween to provide different magnetic paths. The inductor structure at the opposite end of the magnet 20 includes radially extending portions 26 and 21 which have axially extending pole pieces 28 and 29, respectively, positioned so as to cooperate magnetically with the pole faces upon relative rotation therebetween.

In order to produce a large number of flux reversals for one complete revolution of the relatively rotatable member, a particular number of pole faces on the core structure which are situated in a particular manner, are provided. Thus, in the embodiment illustrated in Figs. 1 to 3, inclusive, six pole faces are provided, three extending from each of the arms l2 and I3 which are so situated as to cooperate with four pole pieces to produce a passage of flux through the coil threading portion ll in order to excite the coil structure [0. Adjacent pole pieces of the magnet structure are of opposite polarity and are disposed or circumferentially spaced apart at right angles, and the pole faces of each of the arms l2 and I3 have a pitch equal to two thirds, that is, an even number of thirdsof the angle a between adjacent north and south pole pieces, or degrees. Thus, the pole pitch between the pole faces l4 and I5, and I5 and I6, is equal to 60 degrees and similarly the pole pitch between the pole faces I! and I8, and I8 and I8, is also equal to 60 degrees. Furthermore, the distance between a portion of the pole face I4 and a similar portion of the pole face I! is equal to onethird, that is, an odd number of thirds of the angle between adjacent pole pieces or 30 degrees. Given the above mentioned angular dimensions it will be seen that the pole pitch between the pole faces I6 and will be equal to 90 degrees, or equal to the angle between adjacent pole pieces.

Operation of the magneto illustrated in Figs. 1, 2, and 3 is as follows: Let us assume that the rotating magnetic structure has at any instant a position illustrated by that shown in Fig. 1. Let us further assume that the magnet 20 is so magnetized that the end touching the inductor portions 22 and 23 is the north pole while the end touching the inductor portions 26 and 21 is the south pole. Thus, the pole pieces 24 and 25 may be considered as north poles, while the pole pieces 28 and 29 may be considered as south poles. The magnetic circuit for the flux is, therefore, shown by the arrows in Fig. 1 and may be traced from the north pole 24, through the pole face I4, through the portion II from right to left, to the pole face l8, and through the pole piece 29, back to the opposite end of the magnet 20. Upon rotation of the rotatable magnet structure 20 through an angle equal to 30 degrees, as shown in Fig, 2, the north pole 25 will be opposite a pole face on the other core arm. or the pole piece H of the arm I3. Thus, the flux may pass from the north pole 25 into the pole face I 1, through the portion ll of the core in the opposite direction to the previous passage, and back to the magnet through the pole face and the pole piece 28. When the magnet structure has rotated another 30 degrees as shown in Fig. 3, the north pole 24 will be opposite the pole face l5 and the south pole 29 will be opposite the pole fa'ce l9, so another flux reversal results, as indicated by the arrows. When the magnet structure has rotated another 30 degrees the north pole 25 will be adjacent the pole face l8 while the south pole 29 will be adjacent the pole face M. The passage of flux every 30 degrees for 360 degrees may be plotted as is done for three positions illustrated in Figs. 1, 2, and 3, and it will be seen that 12 flux reversals will be produced for one complete revolution of the magnet structure 20. It will, therefore, be seen that given any suitable even number of pole faces distributed to cooperate with a magnetic structure having at least four pole pieces, twice as many flux reversals through the coil will be produced for one revolution of the rotatable structure as there are pole faces.

In the modification of my invention illustrated in Figs. 4, 5, and 6, twelve circumferentially or angularly spaced apart pole faces of the core structure are provided, so that given a magnet structure with at least four pole pieces suitably angularly disposed or circumferentially spaced apart to cooperate with the pole faces,

twenty-four flux reversals, or an amount equal to twice the number of pole faces, are obtained. However, in the arrangement illustrated eight pole pieces are provided which extend from the magnet structure so as to provide a large amount of flux to link the coil each time the magnetic circuit is completed. Referring to Figs. 4, 5, and 6 the magnet structure 20' has four inductors with arms 30, 3|, 32, and 33 extending from one end, and four inductors with arms 34, 35, 36, and 3'|, extending from the opposite end of the magnet. Thus, four north poles will be provided by pole pieces 38, 39, 40, and 4|, while an equal number of south poles will be provided by pole pieces 42, 43, 44, and 45. The arm l2 of the core member is'provided with six pole faces 46 to 5|, inclusive, while the arm l3 has an equal number of pole faces 52 to 51, inclusive. In the structure illustrated in Figs. 4 to 6, the angle between adjacent pole pieces is 45 degrees, the pole pitch between adjacent pole faces of each of the arms l2 and |3' is 30 degrees, the pole pitch between pole faces 46 and 51 is 15 degrees, and that between the pole faces 5| and 52 is 45 degrees.

Operation of the magneto illustrated in Figs. 4, 5, and 6 is as follows: With the magnet structure at any instant in the position as illustrated in Fig. 4, and with the pole pieces 38, 39, 40 and 4| north poles and with the remaining pole pieces south poles, the magnetic circuit for the flux is illustrated by the arrows and may be traced from the north poles 38 and 40, through the pole faces 46 and 49, through the portion II from right to left and linking the coil |6 to the pole faces 56 and 53, and through the pole pieces 42 and 44 back to the other end of the magnet. Upon rotation of the rotatable magnet structure 20' through an angle equal to 15 degrees, as shown in Fig. 5, the north poles 39 and 4| are opposite the pole faces 52 and 55, respectively, while the south poles 45 and 43 are opposite the pole faces. 48 and 5|, respectively, so that the passage in flux is through the core portion II in the opposite direction from that illustrated in Fig. 4. It will be seen from Fig. 6 that a further rotation of the magnet structure will again provide for passage of fiux through the core portion H from right to left. The passage of flux every 15 degrees for 360 degrees may be plotted as is done in the three positions illustrated. in Figs. 4, 5, and 6, and it will be seen that twentyfour flux reversals will be produced for one complete revolution of the magnet structure 20'.

I wish to point out that only four pole pieces need be provided, two connected to one end of the magnet and two connected to the opposite end of the magnet. Thus, assuming that the magnet structure is provided only with inductor arms 30 and 3| at one end and arms 36 and 31 at the other end; north pole pieces 38 and 38 and south pole pieces 44 and 45 would be provided. With such a structure a flux path is completed every 15 degrees, so that twenty-four flux reversals will be provided for one complete revolution of the magnet structure. Of course, with this structure only one set of poles, one north and one south pole will be available to cooperate with one pole face respectively on each side of the stationary core structure during each time the flux ath is completed instead of two north and two south poles, when a magnet structure is employed as illustrated in Figs. 4, 5, and 6. uch a rotatable magnet structure may be particularly desirable when my invention is applied to a magneto for producing dual ignition. Such a core structure may be provided having core arms extending in opposite directions, as is illustrated in Fig. 7. Thus, a core is provided having arms 58 and 59, and portions 60 and 6| which thread coils 62 and 63, respectively. A rotatable magnet structure 20' is provided for cooperating with the pole faces of the arms 58 and 59. With such a construction, each time a flux path is completed there will be a parallel circuit.- so that the flux may link both the coils simultaneously. It

will, of course, also be apparent that the magneto illustrated in Figs. 1, 2, and 3 may also be provided for dual ignition.

In view of the foregoing, it will be seen that any suitable number of pole pieces and pole faces may be provided and so situated that the desired number of flux reversals may be obtained for one complete revolution of the rotatable structure. Although I have shown the magnet structure as rotatable and the core structure as stationary it may be apparent that this condition may be reversed.

Modifications of the particular arrangements which I have disclosed embodying my invention will occur to those skilled in the art, so that I do not desire my invention to be limited to the particular arrangements set forth and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A dynamo-electric machine including a stationary member having a coil member and a core member magnetically coupled therewith, said core member having six spaced apart pole faces, and means including a rotatable member having a permanent magnet and four spaced apart pole pieces having a pole pitch relative to the pitch of said core pole faces for cooperating on rotation thereof with said pole faces to produce twelve flux reversals through said coil for each revolution of said rotatable member, the pitch of said pole faces on either side of said core member being an even number of thirds of the pole pitch of said pole pieces.

2. A dynamo-electric machine including a coil member and a core member magnetically coupled therewith, said core member having six spaced apart pole faces, and means including a magnet having four spaced apart pole pieces having a pole pitch relative'to the pitch of said core pole faces for cooperating with said pole faces upon relative rotation therebetween to produce twelve flux reversals through said coil for each revolution between said relatively rotatable parts, the pitch of said pole faces on either side of said core member being an even number of thirds of the pole pitch of said pole pieces.

3. A dynamo-electric machine including a stationary member having a coil member and a core member magnetically coupled therewith, said core member having twelve spaced apart pole faces, and means including a rotatable member having a permanent magnet and eight spaced apart pole pieces having a pole pitch relative to the pitch of said core pole faces for cooperating on rotation thereof with said pole faces to produce twenty-four flux reversals through said coil for each revolution of said rotatable member, the pitch of said pole faces on either side of said core member being an even number of thirds of the pole pitch of said pole pieces.

4. A dynamo-electric machine including a coil member and a core member magnetically coupled therewith, said core member having twelve spaced apart pole faces, and means including a magnet having eight spaced apart pole pieces having a pole pitch relative to the pitch of said core pole faces for cooperating with said pole faces upon relative rotation therebetween so that upon each revolution twenty-four reversals are produced through said coil, the pitch of said pole faces on either side of said core member being an even number of thirds of the pole pitch of said pole pieces.

5. A dynamo-electric machine including a coil member and a core member magnetically coupled therewith, said core member having spaced apart pole faces arranged on each side of said coil, and-a magnet having a plurality of spaced apart pole pieces adapted to cooperate magnetically with said pole faces upon relative rotation therebetween, said pole faces having a pole pitch substantially two-thirds of the pitch of said pole pieces and said pole faces on one side of said coil being arranged substantially an odd number of thirds of the pitch of said pole pieces from pole faces on the other side of said coil such that the number of flux reversals through said coil for ,each revolution being equal to three times the number of pole pieces and twice the number of pole faces.

6. A dynamo-electric machine including a coil member and a core member having a plurality of spaced apart pole faces arranged on each side of said coil, and a magnet having a plurality of circumferentially spaced apart pole pieces adapt ed to cooperate magnetically with said pole faces upon relative rotation therebetween, said pole faces having a pole pitch of substantially an even number of thirds of the pitch of said pole pieces and said pole faces on one side of said coil being arranged substantially an odd number of thirds of the pitch of said pole pieces from pole faces on the other side of said coil such that the number of flux reversals through said coil for one revolution being equal to twice the number of pole faces.

7. A magneto for producing ignition for an internal combustion engine including a coil member and a core member, said core member having a portion threading said coil member and a pair of arms extending from said portion, said arms having an equal number of pole faces disposed in the arc of a circle, and a magnet having a plurality of pole pieces with an angle of a between adjacent north and south pole pieces, said pole pieces being adapted to cooperate magnetically with said pole faces upon relative rotation therebetween, the pitch between adjacent pole faces of each of said arms being equal to twothirds of a and the pitch between a pole face of one arm and the adjacent pole face of the other arm being equal to one-third of a.

LEONARD GRIFFITHS. 

